Someone posted the same question a few days ago. I replied to them with
"Ok, well to be able to talk you need to have a key bound, like was suggested to you. Go to the console and type 'bind q +voicerecord'. Replace the q with whatever key you would like to use. Now to talk just hold down that key and a little microphone icon will appear in the bottom right corner.
Alternately you can add bind "q" "+voicerecord" to your config file or your autoexec.cfg. If you don't have an autoexec.cfg file, then simply go into notepad. Type in bind "q" "+voicerecord", then save the file as autoexec.cfg. Now when the game loads up it will execute that file and add the new bind into your configuration.
You can also setup the voice record button in the normal settings screen for CS. Check all the options and make sure you have Voice Comm enabled.
More commands to do with voice comm are listed below:
"voice_loopback 0
Turns on/off the ability to hear oneself over the voice comm system.
voice_maxgain X
X changes the maximum amount of gain the game engine applies to voice
voice_avggain X
X changes the minimum amount of gain the game engine applies to voice
voice_scale X
Sets in incoming voice volume (above 1 seems to be distorted)
voice_fadeouttime 0.100
How far at the end of the transmission the engine starts to fade out the sound to make end of transmissions sound smoother.
voice_enable 1
Turns on/off voice comm.
voice_dsound 0
Turns on/off usage of DirectSound for voice.
voice_eax 0
Turns on/off EAX support for voice.
voice_overdrive X
How much ingame sound will be damped down when someone speaks. X Times quieter
voice_overdrivefadetime : 0.400
Time that the voice communication fades in and out of voice comm
Set to 0 to maintain the same level of game volume (no fading).
voice_recordtofile 0
When set to 1 and you use your voicerecord button two files are created in you half-life directory, voice_decompressed.wav and voice_micdata.wav
voice_inputfromfile 1
(Warning: this may get you banned from some servers)
(server must allow uploads, and client must allow downloads and uploads)
Whenever you press your voicerecord button it plays the file titled"voice_input.wav" from your half-life directory. The files have to be 8kHz 16bit Mono to sound like they are supposed to.
Use Windows Sound Recorder to convert the wav to the proper format.
voice_modenable : 0
Enable(1)/Disable(0) voice for a specific mod
voice_clientdebug : 0
Prints out extra info to the console or a file like (developer "1") command" (from the CS Tech Guide)
Good luck."
You can always use the search function to see if people have already asked the same questions you have.